The invention is based on a priority application EP 04292052.0 which is hereby incorporated by reference
The present invention relates to wireless communication systems, and more particularly, to data flow control in a mobile communications system.
The third generation (3G) evolution of Global Systems for Mobile communications (GSM) networks, commonly known as Universal Mobile Telecommunications Systems (UMTS), introduces High Speed Downlink Packet Access (HSDPA) to provide data rates up to approximately 10 Mbps to support packet-based multimedia services.
UMTS HSDPA capable systems support an additional transport channel type in the downlink direction, a High Speed Downlink Shared Channel (HS-DSCH). This logical channel provides the logical transport mechanism for data transfer.
Currently the 3rd Generation Partnership Project (3GPP) is undertaking the technical specification of HSDPA. 3GPP specification TS 25.435 v5.6.0, 2003-12, provides a description of the interface between a radio network controller (RNC) and a base station, being referred to as the Iub interface. In such document, and more specifically, in chapter 5.1.6, a data transfer procedure is defined for the transmission of HS-DSCH data frames from the RNC to the base station. A mechanism to control user data flow between the RNC and the base station is also implicit in such procedure.
Since the actual transport capacity on the Iub interface is limited, due to the fact that the base station will be connected to the RNC via one or several physical communication links, such as 2.048 Mbps (E1) links or 155 Mbps (STM-1) links, a disadvantage of the specified state of the art RNC-base station user data flow control approach is that it only controls individual user data flows, that is, how much HSDPA traffic an individual user can receive from the RNC. Based on the distribution of the user terminals and the quality of the air interface for a radio cell with HSDPA traffic and in case, for example, the base station needs to serve several of such cells, there is the probability that the total data transport flow in the Iub interface, that is the sum of all individual user data flow instances, exceeds the maximum available Iub interface transport capacity, i.e. a capacity overload situation occurs at the Iub interface.